This invention relates to an earphone or a hearing aid which provides greater fidelity in the reproduction of music and other sound. As used herein, the word "earphone" is intended to include, within its meaning, the similar part of a "hearing aid". The device of the invention may be used by persons with normal hearing, desiring greater fidelity sound, particularly music; and it may also be used by those who have hearing impairment and need a hearing aid in order to hear.
Some of the effects desired to be achieved in presentation of sound to the auditory canal of the ear, or to any location, are, little distortion, little or no undesirable, acoustic or other feedback, and, normally, linear amplification. Often, an earphone or a hearing aid will provide sound with a hollowness, as if being heard through a tube. Other systems do not reproduce the low or the high frequencies adequately. In many devices of the prior art, distortion is found to occur.
When the pressure inside the auditory canal was vented to the atmosphere (the ambient air, or air outside the canal or outside the ear), it substantially improved the performance of hearing aids but also introduced some problems. The sound from the vent path was often picked up by the input microphone and this caused excessive feedback which led to squealing or ringing. Various dampers in the sound delivery paths and in the vent paths reduce the sensitivity of hearing aids to feedback and allow compromise and adjustment to the specific needs of the user.